bio 13

different set of hormones

-involved in organizational(developmental) and activational aspects of sexual behavior

-releases hormones involved in the body's response to stress

-also releases hormones involved in growth

released withing the hypothalamus that flow down to the anterior pituitary

1. hypothalamic hormones are released into a capillary netwrk.

2. these hormones travel down through portal vein in pituatry stalk. hormones either excite or inhibit other hormones of anterior pituatry to be relasesd into bloodstream

• releasing factors
• *it makes the anterior pituatary gland to release hormones.

1. released by hypothalamus travels to the anteiror pit. where it promotes release of thyrotropin

2. Thyrotropin reaches the thymus gland and causes it to release other hormones into the general blood stream, which acts on ither organs to sitmulate metabolism

• 1.causes the anterior pit. to release gonadotropin hormones
• *follicle-stimulating hormone
• *luteinizing hormone

^these hormones act on the gonads, to cause a release of hormones there

males= testes

females= ovaries

-androgens (testosterone)

-estrogens (estradiol)

• *both male and females gonads release these hormones but
• males: androgens> estrogens
• females: estrogens> androgens

-neural

-hormonal

-non-hormonal chemicals

-all glands except anterior pit. are affected by neural inputs

-pineal and post. pit. glands receive inputs form areas in the brain

-other glands receive inputs from the autonomic (peripheral) nervous system

• -provides feedback
• *ex) high levels of androgens reeased by testes could be sensed by brain to shut off further release of gonadotropin-releasing hormone

-small testicles in males taking artificial androgens

-glucose (sugar) can cause the release of the hormone insulin from the pancreas

• *all begin with primordial gonad
• **it can go into testes or ovaries

-medulla and cortex

medulla: potential to develop into testis

cortex: into an ovary

•  6 weeks post conception, Y chrom. causes production of Sry protein
• *causes medulla of primordial gonad to turn into testes

person will develop testes

person will develop ovaries

-wolffian system

-mullerian system

• can fevelop into male ducts
• *seminal vesicles and vas deferens

• can develop into female ducts
• *uterus and fallopian tubes

testes begin to secrete the hormones testosterone and mullerian-inhibiting susbtance

male internal reproductive structures will develop

• Mullerian system will develop on its own and the wolffian system will not develop
• *ovaries are not active during development

-adult females have a cyclical pattern of gonadotropin release

-adult males have a steady release of gonadotropins

the development of the brain

time of birth

• testosterone and estradiol
• *especially estradiol

**testosterone can be easily converted into estradiol by aromatase

-injectons of estradiol can masculanize the hypothalamus

• -dihydrotestosterone fails to masculinize the hypothalamus
• *an androgen that cannot be cnoverted into estradiol

-agents that block the conversion of testosterone to estradiol block the masculinization of the hypothalamus

-ovaries secrete almost no estradiol during development

• -around time of birth, we have a factor circuating our blood called alpha-fetoprotein
• *it binds to estradiol and prevents it from reaching the brain

• - alpha fetoprotein cannot cross the blood-brain barrier
• *its actions are strictly on peripheral

• -alpha fetoprotein binds estrogen not testosterone
• *testosterone can get past this, and cross blood-brain barrier and reach the brain.

critical for future physiological characteristics of males and females as well as future sexual behavior

*however tehre is a long delay until they are sexually active

activational effects

***release of hormones in mature animals can directly lead to changes in sexual behavioer

• -leads to reduction and most often a cessation of sex behavior
• *presumed to be a result of loss of testosterone

**testostorone injections cna restore sexual behaviors

-sexual vigor does not seem to correlate with total amount of circulating testosterone

**when small amount of testostorne is added, it is sufficient to restore one's sexual life

medial preoptic area of the hypothalamus (mPOA)

• abolished male copulatory behavior
• **andorgen implants here in castrated males restores copulation of males

motor-related regions of the brain which project to the spinal cord to produce motor sequences involved in male copulatory behavior

• behavioral estrus
• *cyclical thign

receptive to males at any time

• lordosis
• *elevated rump
• *tail deflected one side
• ***easy access for the male rat

no lordosis

-ventromedial nucleus of the hypothalamus (VMN)

-periaqueductal gray (PAG)

-medullary reticular formation 

the VMN induce lordosis

• *lesions of VMN wipes out lordosis
• *electrrical stimulation of the VMN promotes lordosis